Ординатура / Офтальмология / Английские материалы / Essentials of Ophthalmic Lens Finishing, 2nd edition_Brooks_2003

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lens, negative lenticular A high-minus lens that has had the peripheral portion flattened for the purpose of reducing weight and edge thickness. (Synonym: myodisc.)

lens, Percival form A lens design that concentrates on the elimination of power error instead of oblique astigmatism.

lens, photochromic A lens that changes its transmission characteristics when exposed to light.

lens, plus cylinder form A lens ground so that it obtains its cylinder power from a difference in surface curvature between two front surface meridians.

lens, point focal A lens design that concentrates on the elimination of oblique astigmatism instead of power error.

lens, polarizing A lens that blocks light polarized in one plane, such as light reflected from a smooth, nondiffusing surface.

lens, prism segment A 10-mm deep ribbon-style segment containing a prismatic effect for near. The ribbon segment extends to the nasal edge of the lens blank.

lens, progressive-addition A lens having optics that vary in power gradually from the distance to near zones. lens, quadrafocal A multifocal lens that has a flat-top

trifocal segment in the lower portion of the lens and an inverted flat-top bifocal-type segment in the upper portion of the lens.

lens, reverse-slab A slab-off lens that has base-down prism below the slab line, instead of base-up. Reverseslab lenses are usually precast plastic.

lens, single-vision A lens with the same sphere and/or cylinder power throughout the whole lens, as distinguished from a multifocal lens.

lens, spheric lenticular A lenticular lens whose optically usable central portion has a front surface that does not vary in curvature but is entirely spherical.

lens, stock A lens that is premade and does not have to be custom surfaced.

lens, uncut A lens that has been surfaced on both sides but not yet edged for a frame.

lens, X-Chrom A red contact lens used in an attempt to improve color vision for certain red-green color defectives.

lens, Younger seamless Trade name for a blended bifocal made by Younger Optics.

lenses, iseikonic A lens pair with their curvatures and thicknesses specially chosen in order to produce a difference in image magnification between the left and right eyes. Also known as size lenses.

lensmaker’s formula See formula, lensmaker’s. lensmeter The instrument used for finding power

and prism in spectacle lenses.

lensometer A trade name for a type of lensmeter.

GLOSSARY

lenticular A high-powered lens with the desired prescription power found only in the central portion. The outer carrier portion is ground so as to reduce edge thickness and weight in minus prescriptions and center thickness and weight in plus prescriptions.

lenticular lens See lens, lenticular or lenticular. lenticular, aspheric A lenticular lens whose optically

usable central portion has a front surface with a changing radius of curvature.

lenticular, hand-flattened A negative lenticular lens with the lenticular portion produced on a hand edger and hand polished.

lenticular, negative A high-minus lens that has had the peripheral portion flattened for the purpose of reducing weight and edge thickness. (Synonym: myodisc.) lenticular, spheric A lenticular lens whose optically usable central portion has a front surface that does

not vary in curvature but is entirely spherical.

level, reading A synonym for reading depth. See depth, reading.

library temple See temple, library. light box See box, light.

line, 180-degree A synonym for horizontal midline. line, cutting the 180-degree line marked on a lens after

it has been properly positioned for cylinder axis orientation and decentration. It is used for reference in blocking and edging a lens.

line, datum A line drawn parallel to and halfway between horizontal lines tangent to the lowest and highest edges of the lens. (Synonyms: horizontal midline, 180-degree line.)

line, isocylinder One of the lines on the contour plot of a progressive addition lens denoting the location of unwanted cylinder of a given dioptric power.

line, mounting 1. The horizontal reference line that intersects the mechanical center of a lens pattern. 2. On metal or rimless spectacles the line that passes through the points at which the guard arms are attached, and that serves as a line of reference for horizontal alignment.

liner, figure-8 A liner that that fits into the top eyewire channel of some nylon cord frames.

longitudinal chromatic aberration See aberration, longitudinal chromatic.

LTB The length-to-bend measure of a frame temple.

M

marker A centering device used to accurately position a lens and stamp it with horizontal and vertical reference lines for use in accurate lens blocking.

GLOSSARY

marker/blocker A device used to accurately position a lens and either stamp it with horizontal and vertical reference lines for use in accurate lens blocking, or block it directly while still in the device; that is, a centering device with stamping and blocking capability.

Material Safety and Data Sheet A single sheet of paper containing information about potentially hazardous chemicals found in the workplace. MSDS sheets should include physical and chemical characteristics, known acute and chronic health effects, exposure limits, precautionary measures, and emergency and first-aid procedures.

MBL Minimum between lenses

MBS Minimum blank size. See size, minimum blank. mean dispersion See dispersion, mean.

measure, lens A small, pocket-watch–sized instrument for measuring the surface curve of a lens. Also called a lens clock or lens gauge.

meniscus lens See lens, meniscus.

meridian, axis The meridian of least power of a cylinder or spherocylinder lens; for a minus cylinder the least minus meridian, for a plus cylinder the least plus meridian.

meridian, major One of two meridians in a cylinder or spherocylinder lens. These meridians are 90 degrees apart and correspond to the maximum and minimum powers in the lens.

meridian, power The meridian of maximum power of a cylinder or spherocylinder lens; for a minus cylinder the most minus meridian, for a plus cylinder the most plus meridian.

metal bonded wheel See wheel, metal bonded. metal saddle bridge See bridge, metal saddle. mid-datum depth See depth, mid-datum.

midline, horizontal In the boxing system of lens measurement, the horizontal line halfway between the upper and lower horizontal lines bordering the lens shape. (Synonym: 180-degree reference line.)

mini-bevel A lens edge configuration that has a bevel and an angled ledge.

minimum between lenses The datum system equivalent of the boxing system’s distance between lenses (DBL).

minus add bifocal Bifocal, minus add. minus cylinder form See form, minus cylinder.

minus cylinder form lens See lens, minus cylinder form. minus lenticular lens See lens, minus lenticular.

mirror coating See coating, mirror.

Monel A whitish, pliable, nicely polishing metal frame material that is made from nickel, copper, and iron; it also contains traces of other elements.

monochromatic aberration See aberration, monochromatic.

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monocular PD See PD, monocular.

mounting 1. The name for a spectacle lens frame when the lenses are held in place without the aid of an eyewire as with rimless or semi-rimless mountings. 2. The attaching of lenses to a rimless or semi-rimless spectacle frame.

mounting line See line, mounting.

mounting, Balgrip A mounting (frame) that secures the lens in place with clips attached to a bar of tensile steel that fits into a nasal and a temporal slot on each side of the lens.

mounting, Ilford Synonym for Balgrip mounting. mounting, numont A lens mounting that holds the

lenses in place only at their nasal edge. The lenses are attached at the bridge area and the temples are attached to a metal arm that extends along the posterior surface temporally. Thus each lens has only one point of attachment.

mounting, rimless A mounting that holds the lenses in place by some method other than eyewires or nylon cords. Usually the method of mounting is by screws through the lenses. (Synonym: three-piece mounting.)

mounting, semirimless Mountings similar to the rimless, except for a metal reinforcing arm, which follows the upper posterior surface of the lens and joins the centerpiece of the frame to the endpiece.

mounting, Wils-Edge A lens mounting (frame) that secures the lens in place by means of a grooved arm that grips the top of the lens.

MRP An abbreviation for major reference point. See point, major reference.

MSDS Abbreviation for Material Safety and Data Sheet. multidrop lens See lens, multidrop.

multifocal A lens having a sector or sectors where the refractive power is different from the rest of the lens, such as bifocals or trifocals.

multifocals, segmented Multifocal lenses having a visible, clearly demarcated bi-or tri-focal area. Nonsegmented multifocals would be progressive addition lenses.

myodisc See lens, myodisc. myope A person with myopia.

myopia The refractive condition of the eye whereby light focuses in front of the retina. Minus lenses are required to correct for myopia. (Synonym: nearsightedness.)

N

nasal The side of a lens or frame that is toward the nose (inner edge).

nasal add See add, nasal. nasal cut See cut, nasal.

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NBC The abbreviation for nominal base curve. near power See power, near.

near reference point See point, near reference.

near Rx The net power resulting from the combination of the add power and the distance power.

nearsightedness See myopia. net seg inset See inset, net seg.

neutralize To determine the refractive power of a lens. Most often this is done with the aid of a lensmeter. neutralizer A solution used to reduce the color in or

remove the color from a previously tinted lens. nickel silver A whitish-appearing metal frame mate-

rial containing more than 50% copper, 25% nickel, and the rest zinc. (Synonym: German silver.)

nominal base curve See curve, nominal base.

normal A line perpendicular to a reflecting or refracting surface at the point of incidence.

NRP An abbreviation for near reference point. See point, near reference.

number, set The compensating number used with a pattern to arrive at a compensated eyesize setting for the edger.

Numont mounting See mounting, Numont. Numont pliers See pliers, Numont.

nystagmus A condition characterized by a constant, involuntary back-and-forth movement of the eye.

O

oblique astigmatic error See error, oblique astigmatic. oblique astigmatism See astigmatism, oblique.

OC Optical center.

Occupational Health and Safety Administration The U.S. government agency responsible for setting workplace safety policy and ensuring worker safety.

OD Latin, oculus dexter (right eye).

OLA Abbreviation for the Optical Laboratories Association.

open temple spread See spread, open temple.

opening, lens The portion of the spectacle frame that accepts the spectacle lens. (Synonym: lens aperture.)

optical axis See axis, optical. optical center See center, optical.

Optical Laboratories Association A professional asso-

Optyl The trade name for an epoxy resin material used to make spectacle frames.

OS Latin, oculus sinister (left eye).

OSHA Occupational Health and Safety Administration.

outset The amount of lens decentration temporally

GLOSSARY

from the boxing center of the frame’s lens aperture. (Antonym: inset.)

overall temple length See length, overall temple.

P

p Symbol for the GOMAC system distance between lenses. It is equal to the boxing DBL.

pad arms See arms, pad.

pad-adjusting pliers See pliers, pad-adjusting.

pads, build-up Small nosepad-shaped pieces of plastic used to alter the fit of the bridge.

Panoptik See bifocal, Panoptik.

pantoscopic angle or tilt See angle, pantoscopic. pantoscopic angling pliers See pliers, pantoscopic

angling.

parallax The apparent change in position of an object as the result of a change in viewing angle.

paraxial rays See rays, paraxial.

pattern difference See difference, pattern.

pattern A plastic or metal piece having the same shape as the lens aperture for a given frame. Used in lens edging as a guide for shaping the lens to fit the frame.

pattern, geometrically centered A pattern with mechanical and geometrical centers on the same horizontal plane.

pattern, optically centered A pattern with its mechanical center above boxing center.

patterned edger See edger, patterned. patternless edger See edger, patternless.

PD An abbreviation for interpupillary distance (see distance, interpupillary).

PD, binocular The measured distance from the center of one pupil to the center of the other pupil without regard to how each eye may vary in its distance from the center of the bridge of the frame.

PD, distance The wearer’s interpupillary distance specified for a situation equivalent to when the wearer is viewing a distant object.

PD, frame Synonym for geometrical center distance or distance between centers.

PD, monocular Interpupillary distance specified for each eye individually. The center of the frame bridge is the reference point from which measurements are specified.

PD, monocular The distance from the center of the frame bridge to the center of the wearer’s pupil measured for each eye separately.

PD, near The interpupillary distance as specified for a near viewing situation.

Percival form lens See lens, Percival form. peripheral rays See rays, peripheral.

GLOSSARY

phoria The direction of the line of sight of one eye with reference to that of the partner eye when fusion is interrupted, as when one eye is covered.

photochromic lens See lens, photochromic.

photometer An instrument for measuring brightness. When used with lenses, the percent transmission of the lens is measured in a given spectral area or areas.

pillar file See file, pillar.

pincushion distortion See distortion, pincushion. planes, variant A form of vertical misalignment of a

spectacle frame in which the lens planes are out of coplanar alignment (one lens is further forward than the other).

plano (pl) A lens or lens surface having zero refracting power.

pliers, bridge-narrowing Used to narrow the bridge of a plastic frame.

pliers, bridge-widening Used to widen the bridge of a plastic frame.

pliers, chipping Pliers used to chip or break away the outer portions of an uncut or semifinished glass lens to either reduce its size or bring it into the rough shape needed to approximate the finished shape.

pliers, endpiece angling Pliers used in the adjustment of rimless mountings.

pliers, eyewire-forming Pliers with horizontally curved jaws used to shape or form the upper and lower eyewires of a metal frame to match the meniscus curve of the edged lens.

pliers, fingerpiece Pliers used for adjustment of the temple-fold angle of plastic frames. Fingerpiece pliers have parallel jaws and were originally designed for adjusting fingerpiece mountings. Also called Fits-U pliers.

pliers, hollow snipe-nosed Thin-nosed pliers with a hollowed-out central jaw area.

pliers, Numont Holding pliers specially designed for use with Numont mountings. Numont pliers serve the same purpose for Numont mountings as endpiece angling pliers do for standard rimless mountings.

pliers, pad-adjusting These pliers have one cupped jaw to conform to the face-portion of an adjustable nosepad; the other jaw is shaped to allow the back of the pad to be held securely while being angled.

pliers, snipe-nosed Pliers that taper to a small tip on both jaws, allowing use in tight places. Often used in the adjustment of pad arms.

pliers, square-round Used to adjust pad arms, these pliers have a small round section on one jaw and a squared off section on the other.

pliers, strapping Pliers having two flat jaws. One jaw extends beyond the other and then overlaps it. Used to adjust straps of a rimless or semirimless mounting. plot, contour A line diagram used to plot the areas of

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unwanted cylinder, attainable visual acuity, or vertical imbalance over the viewing areas of a progressive addition lens.

plus cylinder form See form, plus cylinder. plus-cylinder-form lens See lens, plus cylinder form. point One tenth of a millimeter of lens thickness. point focal lens See lens, point focal.

point, distance centration The British equivalent of the major reference point.

point, distance reference (DRP) That point on a lens where, according to the manufacturer, the distance power is to be measured. Distance power consists of sphere, cylinder and axis. DRP may not correspond to the prism reference point (PRP), as with progressive addition lenses.

point, focal A point to or from which light rays converge or diverge.

point, major reference (MRP) The point on a lens where the prism equals that called for by the prescription.

point, near reference (NRP) That point on the lens where, according to the manufacturer, the power of the near addition is to be measured.

point, prism reference (PRP) The point on a lens where prism power is to be verified. Also referred to as the major reference point.

polariscope See colmascope. polarizing lens See lens, polarizing.

polyamide A strong, nylon-based frame material that allows a frame to be made thinner and lighter than it would ordinarily be if made from cellulose acetate frame material.

polycarbonate A 1.586-index lens material known for its strength.

power cross See cross, power.

power meridian See meridian, power. power, actual Synonym for true power.

power, back vertex The reciprocal of the distance in air from the rear surface of the lens to the second principal focus, which serves as a specific measure of the power of a lens.

power, chromatic See aberration, lateral chromatic. power, compensated Back vertex power that has been

converted to a 1.53-index frame of reference. Used for the purpose of finding a 1.53-index-referenced tool curve for a lens with a different index of refraction.

power, dispersive The following quantity

nF – nC

nD – 1

used for quantifying chromatic aberration of a given material. Dispersive power is abbreviated as the Greek letter omega, or ω.

power, effective 1. The vergence power of a lens at a

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designated position other than that occupied by the lens itself. 2. That power lens required for a new position that will replace the original reference lens and yet maintain the same focal point.

power, focal A measure of the ability of a lens or lens surface to change the vergence of entering light rays. power, front vertex The reciprocal of the distance in air from the front surface of a lens to the first

principal focus.

power, near The sum of the distance power and the near add. (Synonym: near Rx.)

power, nominal An estimate of total lens power, calculated as the sum of front and back surface powers. (Not to be confused with nominal base curve.)

power, refractive The dioptric value that accurately describes the ability of a lens or lens surface to converge or diverge light. For a lens surface in air the refractive power is expressed as

F =

n – 1

r

where n is the refractive index of the lens material and r is the radius of the surface expressed in meters. power, true The 1.53-index-referenced curvature of the base curve of a lens. True power is found by using a lens clock or sagometer (sag gauge) that is 1.53-

index referenced.

precoat A spray or brush-on liquid that when applied to a lens, protects the surface during processing, and/or makes the adhesion of a block to the lens possible.

Prentice’s Rule See Rule, Prentice’s.

Prep, Lens A trade name for lens conditioner.

prism That part of an optical lens or system that deviates the path of light.

prism axis See axis, prism. prism diopter See diopter, prism.

prism reference point See point, prism reference. prism, Fresnel A prism made from thin flexible mate-

rial and consisting of small rows of equal-powered prisms resulting in the same optical effect as that of a conventional ophthalmic prism.

prism, Rx Prism in an ophthalmic lens prescription that has been called for by the prescribing doctor. prism, yoked Vertical prism of equal value ground on

both right and left lenses of a progressive or Franklinstyle lens for the purpose of reducing lens thickness. progressive-addition lens See lens, progressive-addition. propionate The common name for the frame material cellulose aceto-propionate. Propionate has many of the same characteristics as cellulose acetate and is

better suited for injection molding.

protractor, lens A millimeter grid on a 360-degree protractor used in the lens centration process for both surfacing and finishing.

GLOSSARY

PRP An abbreviation for prism reference point. See point, prism reference.

Q

quadrafocal See lens, quadrafocal.

R

radial astigmatism See astigmatism, oblique.

raise, seg 1. The vertical distance from the major reference point to the top of the seg when the seg top is higher than the MRP. 2. The vertical distance from the horizontal mid-line of the edged lens to the top of the seg when the seg top is higher than the horizontal midline (laboratory usage). (Antonym: seg drop.)

rat-tail file See file, rat-tail.

rays, paraxial Those rays of light that pass through the central area of the lens.

rays, peripheral Those rays of light that enter the lens nearer the edge than the center.

R-compensated segs See segs, R-compensated. reading center See center, reading.

reading depth See depth, reading. reading level See level, reading. real image See image, real.

Rede-Rite bifocal See bifocal, minus add. reduced thickness See thickness, reduced.

refraction 1. The bending of light by a lens or optical system. 2. The process of determining the needed power of a prescription lens for an individual.

refractive index See index, refractive. refractive power See power, refractive.

single prism as two prisms whose base directions are perpendicular to each other but whose combined effect equals that of the original prism.

retroscopic angle or tilt See angle, retroscopic. reverse-slab lens See lens, reverse-slab.

ribbon bifocal See bifocal, ribbon. ribbon file See file, slotting.

riding-bow temple See temple, riding-bow. riffler file See file, riffler.

rim See eyewire.

rimless Having to do with frames (mountings) that hold lenses in place by some method other than eyewires. Most rimless mountings have two points of attachment per lens.

GLOSSARY

rimless mounting See mounting, rimless. Rimway mounting See mounting, semirimless. rolled edge See edge, rolled.

rolling A pulling of the eyewire such that it covers less of the front of the lens bevel than back or vice versa.

round-seg bifocal See bifocal, round-seg.

Rule, Prentice’s A rule that states that the decentration of a lens in centimeters times the power of the lens is equal to the prismatic effect:

= cF

rule, three-quarter The three-quarter rule states that for every diopter of dioptric demand, the optical center of each reading lens, or the geometrical center of each bifocal addition, should be inset 0.75 (threequarters) mm.

Rx prism See prism, Rx.

S

saddle bridge See bridge, saddle. safety bevel See bevel, safety. safety eyewear See eyewear, safety.

sag A synonym or abbreviation for sagittal depth. See also depth, sagittal.

sagittal depth See depth, sagittal.

scratch A furrowed-out line that has jagged edges. screw extractor See extractor, screw.

second focal length See length, second focal. second principal focus See focus, second principal. seg See segment.

seg clock See clock, seg. seg depth See depth, seg. seg drop See drop, seg. seg height See height, seg. seg inset See inset, seg.

seg optical center See center, seg optical. seg width See width, seg.

segment (seg) An area of a spectacle lens with power differing from that of the main portion.

segment, prism See lens, prism segment. segmented multifocals See multifocals, segmented.

segs, dissimilar A method of correcting vertical imbalance at near that uses different bifocal segment styles for the right and left eyes.

segs, R-compensated A method for correcting vertical imbalance at near that uses ribbon-style bifocal segments that have been modified so that the segment optical center for one lens is high in one segment and low in the other.

semidiameter Diameter divided by 2. In ophthalmic optics, semidiameter refers to half of the chord for

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the arc of a given surface and is used in calculating the sagittal depth of the surface.

semifinished blank See blank, semifinished. semifinished lap tool See tool, semifinished lap. semirimless mountings See mountings, semirimless. semisaddle bridge See bridge, semisaddle.

set number See number, set. shell frame See frame, shell.

shield On a plastic frame, the metal piece to which rivets are attached to hold the hinge in place.

shields, side Protective shields attached to the spectacle frame at the outer, temporal areas to protect the eyes from hazards approaching from the side.

shoe That part of the strap area of a mounting that contacts the edge of the lens, bracing it. Also called shoulder or collar.

shop, back Synonym for surfacing laboratory. shop, front Synonym for finishing laboratory. shoulder See shoe.

side shields See shields, side.

sine For a right triangle, the ratio of the side opposite the angle considered, to the hypotenuse:

Sine =

Opposite

Hypotenuse

sine-squared formula See formula, sine-squared. single-vision lens See lens, single-vision.

size lenses See lenses, iseikonic.

size, lens In the boxing system, the A dimension of a lens or lens opening.

size, minimum blank The smallest lens blank that can be used for a given prescription lens and frame combination.

sizer A frame chassis or frame front used exclusively for checking edged lens size accuracy.

skewed bridge See bridge, skewed. skull temple See temple, skull.

slab-off Grinding a portion of a lens so as to add a second optical center. Often used to create vertical prism in the lower portion of one lens for the purpose of alleviating vertical imbalance at near.

sleek A furrowed-out line on a lens, which resembles a scratch but whose edges are smooth instead of jagged.

slotting file See file, slotting.

smoothing, edge The process of bringing the bevel surfaces of an edged lens to a finer, smoother finish.

Snell’s law See law, Snell’s.

snipe-nosed pliers See pliers, snipe-nosed. solid tint See tint, solid.

spectrophotometer A device used to measure the transmission of each wavelength of light across the spectrum.

sphere (sph) A lens having a single refractive power in all meridians.

386

spheric lenticular See lenticular, spheric. spherical aberration See aberration, spherical. spherical equivalent See equivalent, spherical.

spherocylinder The combination of sphere and cylinder powers into a single lens.

splay angle See angle, splay. sports eyewear See eyewear, sports.

spotting The placing of spots on a lens with a lensmeter in such a manner that the lens will be oriented correctly for axis and positioned for major reference point and horizontal meridian locations.

spread, open temple That angle an open temple forms in relationship to the front of the frame (also called let-back).

square-round pliers See pliers, square-round.

SRC An abbreviation for scratch resistant coating. standard alignment See alignment, standard.

stars Microchips at the lens surface/lens bevel interface.

stock lens See lens, stock.

stock, lens 1. An inventory of lenses. 2. The material from which a semifinished blank is made, as in the amount of stock removal required to bring the blank to its needed thickness.

stone 1. An abrasive grinding wheel. 2. To sharpen the cutting ability of a grinding wheel by honing it with an abrasive stick.

stone, hand Synonym for hand edger.

strabismus The condition whereby one eye is pointed in a different direction than the other eye.

straight-back temple See temple, straight-back.

strap Mechanism for holding drilled lenses in a rimless or semirimless mounting.

strapping pliers See pliers, strapping.

stria A streak seen in a lens caused by a difference in the refractive index in the material. The streak causes a distortion in the object viewed and is not a physical streak like a mark on or in the lens. (The plural of stria is striae.)

surfacing The process of creating the prescribed refractive power, prism, and major reference point location on a lens by generating the required curves and bringing the surface to a polished state.

swarf Fibrouslike lens material resulting from the grinding process for certain types of lens material, such as polycarbonate.

system, boxing A system of lens measurement based on the enclosure of a lens by horizontal and vertical tangents to form a box or rectangle.

system, datum A system of lens measurement that defines the lens or eyesize as being the width of the lens along the datum line and the bridge size as the width of the bridge at the level of the datum line.

GLOSSARY

system, GOMAC A European Economic Community standard incorporating portions of both the boxing and datum systems.

T

tables, sag A set of tables used for finding sagittal depth when surface power and lens diameter are known.

tables, surfacing Tables supplied by a lens manufacturer for the purpose of helping the surfacing laboratory accurately determine the tool curves and lens thicknesses needed to grind lenses to the specified back vertex power. Surfacing tables are now largely replaced by computer software programs.

tangent For a right triangle, the ratio of the side opposite the angle considered to the side adjacent:

Tangent =

Opposite

Adjacent

tap Consists of a chuck on a handle in which threaders of varying size may be placed. It is used to restore threading that has been damaged.

tempering, chemical The process of increasing the impact resistance of glass lenses by immersing them in a bath of molten salt. (Synonyms: chemtempering, chem hardening.)

temple The part of a pair of spectacles that attaches to the frame front and hooks over the ears to hold spectacles in place.

temple, cable Cable temples are of metal construction with the curl, or postear portion, constructed from a flexible coiled cable. The postear portion follows the crotch of the ear where the ear and the head meet and extends to the level of the earlobe. (Synonym: Relaxo.)

temple, comfort cable See temple, cable.

temple, convertible Temples that are straight through their entire length but are designed to be bent down to take on the form of a skull temple.

temple, library The type of spectacle frame temple that begins with average width at the temple butt and increases in width toward the posterior end of the temple. Library temples are practically straight and hold the glasses on primarily by pressure against the side of the head. (Synonym: straight-back temple.)

temple, riding-bow Plastic temples with thin, round postear portions that curve around the ear, following the crotch of the ear where the ear and the head meet and extend to the level of the earlobe. They often are used in children’s and safety frames and are the plastic version of the metal comfort cable temple.

temple, skull The type of spectacle frame temple that

GLOSSARY

bends down behind the ear and follows the contour of the skull, resting evenly against it.

temple-fold angle See angle, temple fold.

temporal The area of a lens or frame that is toward the temples (outer edge).

test, drop-ball A test to determine impact resistance of ophthalmic lenses whereby either a 5/8- or 1-inch steel ball is dropped onto the front surface of the lens from a height of 50 inches.

test, flat surface touch A test for temple parallelism in which the spectacles are positioned upside-down on a flat surface with temples open.

test, high mass impact A pointed, conical-tipped projectile weighing 17.6 ounces is dropped from 51.2 inches through a tube and onto the eyeglasses. The lens must not break, nor come out of the frame. (Note: A proposed change to this test modifies the distance from 51.2 to 50 inches.)

test, high velocity impact This test simulates a highvelocity, low-mass object. In the high velocity impact test a series of 1/4-inch steel balls traveling at 150 feet per second are directed at 20 different parts of the frame with lenses in place. A new frame is used for each impact. Neither the frame for the lens can break. Nor can the lens come out of the frame.

thickness, reduced The thickness of a medium divided by its refractive index.

three-quarter rule See rule, three-quarter.

tint, double gradient A lens tint that has two colors, one at the top and a second at the bottom. The color at the top is darkest at the top and fades out towards the middle of the lens. The color at the bottom is most intense at the bottom and lighten toward the middle.

tint, gradient The variation in light transmission of a lens from a low transmission (dark) to high transmission (light) from one area of the lens to another. Usually the lens is dark at the top and lightens at the bottom.

tint, solid A tint that has the same color and light transmission over the entire lens.

tint, triple gradient A lens with three colors. The color at the top is darkest at the top and fades out toward the middle of the lens. The color at the bottom is most intense at the bottom and lightens toward the middle. The third color is in the middle of the lens.

tongue See ear.

tool, lap A tool used for fining and polishing lens surfaces. The tool used must have a surface identical in curvature to that of the lens for which it is to be used; that is, if the lens surface is convex, the tool must be concave.

toric A surface having separate curves at right angles to one another.

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toric base curve See curve, toric base. toric transposition See transposition, toric. total inset See inset, total.

touch, four-point A check for vertical alignment carried out by placing a straight edge so that its edge goes across the inside of the entire front of the spectacles below the nosepad area.

tracer, frame An instrument used to physically trace the inside groove of a frame’s lens opening or the outside edge of a lens for the purpose of creating a digitized shape. That shape is then transmitted to a patternless edger so that the shape can be duplicated when the lens is edged.

Transitions A trade name for a brand of plastic photochromic lenses.

transmission The percent of light passing on through a lens and out the back surface, compared to the amount of light incident upon the first surface.

transposition, toric The process of transposing a prescription from the form in which it is written to another form, such as from a plus to a minus cylinder form.

treating, heat The process of hardening a glass lens by first heating it in a kiln, then quickly cooling by blowing forced air against both front and back surfaces. (Synonyms: air hardening, heat hardening, heat tempering.)

trifocals Lenses having three areas of viewing, each with its own focal power. Usually the upper portion is for distance viewing, the lower for near, and the middle or intermediate portion for distance in between.

triple gradient tint See tint, triple gradient.

Trivex The brand name for a PPG Industries plastic lens material known for its high impact resistance and ability to be processed in a manner similar to that of other plastic lenses.

true 1. To bring a pair of glasses into a position of correct alignment. 2. To reshape the cutting surface of a worn grinding wheel so that it cuts at the angles and in the manner originally intended. 3. In surfacing, when using a hand pan, a step following roughing and smoothing, using a somewhat finer grade of abrasive in order to bring the lens to an exact curve.

true base curve See curve, true base. true power See power, true.

trueing See true.

Tscherning ellipse See ellipse, Tscherning. turn-back endpiece See endpiece, turn-back.

U

ultraviolet Rays having a wavelength somewhat shorter than those at the violet end of the visible spectrum.

388

uncut A lens that has been surfaced on both sides but not yet edged for a frame.

upcurve bifocal See bifocal, minus add. UV index See index, UV.

V

value, Abbé The most commonly used number for identifying the amount of chromatic aberration for a given lens material. The higher the Abbé value, the less chromatic aberration present in the lens. Abbé value is the reciprocal of ω (dispersive power) and is the symbolized by the Greek letter nu, or ν. In other words:

ω1 = ν

(Synonyms: nu value, constringence.) variant planes See planes, variant. V-bevel See bevel, V.

vertex distance See distance, vertex.

vertex power allowance See allowance, vertex power. vertical alignment See alignment, vertical.

vertical angle See angle, vertical.

vertical imbalance See imbalance, vertical.

Vertometer Trade name for a type of lensmeter. virtual image See image, virtual.

W

W bridge See bridge, metal saddle.

washer, lens Also called lens liner, a plastic material that is inserted between a loose lens and the eyewire. wave A defect in lens surface curvature causing a

localized irregular variation in lens power. wave front See front, wave.

wheel differential See differential, wheel.

wheel, electrometallic Synonym for electroplated wheel.

wheel, electroplated An abrasive wheel made by electrolytically depositing metal on the wheel in such a manner as to encompass diamond particles. This type of wheel is often used to grind plastic lenses

wheel, finishing The wheel used in edging to bring the lens edge to its final configuration.

wheel, hogging Synonym for roughing wheel.

GLOSSARY

wheel, impregnated Synonym for a metal-bonded wheel.

wheel, metal-bonded Abrasive wheels made by mixing diamond material with powdered metal that is heated in a mold until fusion of the metal occurs.

wheel, roughing An edger wheel that rapidly cuts a lens to near its finished size.

width, seg The size of a bior trifocal segment measured horizontally across its widest section.

Wils-Edge mounting See mounting, Wils-Edge.

X

X-Chrom lens See lens, X-Chrom.

X-ing A vertical misalignment evidenced by a twisting of the frame front such that the planes of the lenses are out of coincidence with each other.

Y

yoked prism See prism, yoked.

Younger blended myodisc See lens, blended myodisc.

Younger seamless See lens, Younger seamless.

Z

Z80.1 The identification number for the American National Standard for Ophthalmics–Prescription Ophthalmic Lenses–Recommendations.

Z87 The identification number for the American National Standard Practice for Occupational and Educational Eye and Face Protection, denoting safety lenses and frames.

zero inset method See method, zero inset.

zone, blended The blurred area between distance and near areas on an “invisible” bifocal. (Not to be confused with the progressive zone of a progressiveadd lens.)

zone, progressive That portion of a progressiveaddition lens between the distance and near portions where lens power is gradually increasing.

zyl file See file, zyl.

zyl An abbreviation for the frame material zylonite. Often used to refer to plastic frames in general.